Can we just all agree undying life is what it is and call it a day? Personally, I think it's the best spell ever. In fact, if I could only cast two spells ever again, that would be one of them. But I don't want big brother to somehow find this post and change the spell. You either like the spell or ya don't. And if you don't like it, then you don't use it so it isn't a problem. If you do like it, then continue to use it. But this isn't blues clues, we don't need to be brainstorming various situations as to how it's good or not. I'm sure some don't mind getting their classes nerfed by bragging at how awesome they are at it, but us clerics do.
Personally, I opt for a 2h because I think the Erilynne Ornamentation looks ridiculous as a 1h. That is the only reason, as frivolous as that sounds. That being said, most clerics (including myself until I got this ornament) choose a 1h and a shield. Shield AC is better than a raw 2h. We also get 18 ranks of shield block as opposed to only 5 ranks of staff block. I do not have on my cleric, nor do I want to look up the new priest 1h (there are two) and shield, and compare it to my raid 2h. As it stands, my old 1h and shield (Darkened Trakanon's Malleus and Dragon's Honor) have a few more mana points than the 2h. The shield alone has more AC than the 2h. That's with different augs in all three pieces. Honestly it's up to you. I personally do not notice a difference in my cleric's survivability, mana pool, etc between the two. If you have mana problems, then go with a 1h and shield. The Invested Tome of Obulus is pretty good. If you get agro a fair amount and are worried about having time to fade it off, then go with a 1h and a shield. If none of those apply to you and you realize your heals far outweigh any arguments on heal procs, sport a 2h. Ultimately you pay to play your character, play it how ya want.
AC thing is real, but "number of ranks" isn't a good way to compare AA on the blocking. At max ranks (regardless of how many it took to get there), Shield Block is 20%, Staff Block is 15%
Having a few different weapon sets on the bandolier is best. Something with a shield for defense. Something with mana return procs for mana. Something 2handed for DPS. Something with heal procs.